How to split an equation over two lines?

Question

I am new to LaTeX,

Here is my formula,

\documentclass{article}
\begin{document}
    \begin{equation}
        \small{
        \Delta (h)_{T+S} =
        \prod_{j=1}^{N} \left[\frac {P(x^j,y^j|\theta_{paired})} 
        {P(x^j,y^j|\theta_{unpaired})}\right]\left[\frac{P(bp)_{x^j,y^j} 
        P(bp_{x^j,y^j}|pbp_{x^{j-1},y^{j+1}}) P(dl_{x^j})  
        P(dl_{x^j}|pdl_{x^{j-1}})P(dr_{y^j})P(dr_{y^j}|pdr_{y^{j+1}})}{P(sl) 
        P(dl|sl) P(sr) P(dr|sr)}\right]}
    \end{equation}
\end{document}

I want the equation to be split over two lines, how can I do this? I tried, multline, align*, split, alignedat, nothing seems to work. Please help me with this. Thank you in advance.

Answer 1

Here there is my proposal to split your equation.

EDIT: The slight change in my code is due an additional \cdot.

\documentclass{article}
\usepackage[margin=2cm]{geometry}
\usepackage{mathtools,amssymb}
\begin{document}
\begin{equation}
\begin{split}
\Delta (h)_{T+S} & =\prod_{j=1}^{N} \left[\frac {P(x^j,y^j|\theta_{\mathrm{paired}})} 
{P(x^j,y^j|\theta_{\mathrm{unpaired}})}\right] \\
& \cdot \left[\frac{P(bp)_{x^j,y^j} 
P(bp_{x^j,y^j}|pbp_{x^{j-1},y^{j+1}}) P(dl_{x^j}) P(dl_{x^j}|pdl_{x^{j-1}})P(dr_{y^j})P(dr_{y^j}|pdr_{y^{j+1}})}{P(sl) 
P(dl|sl) P(sr) P(dr|sr)}\right]
\end{split}
\end{equation}
\end{document}

Answer 2

The brackets are surplus here, the fraction is a group by itself, so you don't need extra grouping. If I use brackets, I will enclose the whole formula to the right of the = sign into a pair of brackets. I also used \biggl[ and \biggr] for easy splitting. Finally, as @Sebastiano suggested, use \mathrm for text.

Note: you didn't tell us how thick the margins are, so I assumed 1in. If my answer is still too wide, uncomment the \small block.

\documentclass{article}
\usepackage{amsmath}
\usepackage[margin=1in]{geometry}

\begin{document}

%{\small
\begin{equation}
\begin{split} \Delta (h)_{T+S} &= 
\prod_{j=1}^{N} \biggl[\frac {P(x^j,y^j|\theta_\mathrm{paired})} 
{P(x^j,y^j|\theta_\mathrm{unpaired})} \times{} \\
&\phantom{{}={}}\frac{P(bp)_{x^j,y^j} 
P(bp_{x^j,y^j}|pbp_{x^{j-1},y^{j+1}}) P(dl_{x^j})  
P(dl_{x^j}|pdl_{x^{j-1}})P(dr_{y^j})P(dr_{y^j}|pdr_{y^{j+1}})}{P(sl) 
P(dl|sl) P(sr) P(dr|sr)}\biggr]
\end{split}
\end{equation}
%}

\end{document}

Answer 3

A way to put the equation on a single line, with the \splitfrac command from mathtools, the \medmath command from nccmath and some adjustment for the delimiters:

\documentclass{article}
\usepackage[margin=2cm]{geometry}
\usepackage{mathtools, nccmath, amssymb}

\begin{document}

\begin{equation}
\Delta (h)_{T+S} =\prod_{j=1}^{N} \left[\frac {P(x^j,y^j\mid\theta_{\mathrm{paired}})}
{P(x^j,y^j\mid\theta_{\mathrm{unpaired}})}\right]\cdot
 \left[\frac{\medmath{\splitfrac{P(bp)_{x^j,y^j}
P\bigl(bp_{x^j,y^j}\mid pbp_{x^{j-1},y^{j+1}}\bigr)P(dl_{x^j}) }{ P(dl_{x^j}\mid pdl_{x^{j-1}})P\bigl(dr_{y^j}\bigr)P\bigl(dr_{y^j}\mid pdr_{y^{j+1}}\bigr)\rule[-1.5ex]{0pt}{1ex}}}}{P(sl)
P(dl|sl) P(sr) P(dr| sr)^{\strut} }\right]
\end{equation}

\end{document} 

Answer 4

one more alternative, with use of mathtools and nccmath:

\documentclass{article}
\usepackage{geometry}
\usepackage{mathtools, nccmath}

%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\begin{document}
    \begin{equation}
\medmath{
\begin{multlined}
\Delta (h)_{T+S}
    = \prod_{j=1}^{N} \Biggl[\frac{P(x^j,y^j\mid\theta_{\mathrm{paired}})}
                                 {P(x^j,y^j\mid\theta_{\mathrm{unpaired}})}\Biggr]\\
    \cdot \Biggl[\frac{P(bp)_{x^j,y^j} P(bp_{x^j,y^j}\mid pbp_{x^{j-1},y^{j+1}}) P(dl_{x^j}) P(dl_{x^j}\mid pdl_{x^{j-1}})P(dr_{y^j})P(dr_{y^j}|pdr_{y^{j+1}})}
                     {P(sl) P(dl\mid sl) P(sr) P(dr\mid sr)}\Biggr]
\end{multlined}
        }
    \end{equation}
\end{document}

Answer 5

Here's a multlined-based solution. It also uses \mid rather than | to denote conditioning, and it "snugs up" the subscript terms to dr.

\documentclass{article}
\usepackage[a4paper,margin=2.5cm]{geometry} % make suitable page and margin choices
\usepackage{mathtools} % for 'multlined' environment

\begin{document}

\begin{equation}
\renewcommand{\!}{\mkern-2mu} % default: \mkern-3mu
\begin{multlined}
\Delta(h)_{T+S} = \prod_{j=1}^{N} \biggl[
\frac {P(x^j\!,y^j\mid \theta_{\mathrm{paired}})}{%
P(x^j\!,y^j\mid \theta_{\mathrm{unpaired}})}\\
\times
\frac{P(bp)_{x^j\!,y^j}
P(bp_{x^j\!,y^j}\mid pbp_{x^{j-1}\!,y^{j+1}}) 
P(dl_{x^j}) P(dl_{x^j}\mid pdl_{x^{j-1}})
P(dr_{\!y^j})P(dr_{\!y^j}\mid pdr_{\!y^{j+1}})}{%
P(sl) P(dl\mid sl) P(sr) P(dr\mid sr)} \biggr]
\end{multlined}
\end{equation}
\end{document}

Answer 6

With multiline one can insert \\ at the locations where the line should be broken.

Multiletter subscripts ought not be set in math italics, the kerning is wrong. I suggest to warp them in \mathrm{}

The fontsize change needs to be outside the equation and without {} following it. \small was still a bit to large, but with \footnotesize the equation fits even without cheating and changing the margin sizes.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

{
\footnotesize
\begin{multline}
\Delta (h)_{T+S} =
\prod_{j=1}^{N} \left[\frac {P(x^j,y^j|\theta_{\mathrm{paired}})} 
{P(x^j,y^j|\theta_{\mathrm{unpaired}})}\right]\cdot\\
\left[\frac{P(bp)_{x^j,y^j} 
P(bp_{x^j,y^j}|pbp_{x^{j-1},y^{j+1}}) P(dl_{x^j})  
P(dl_{x^j}|pdl_{x^{j-1}})P(dr_{y^j})P(dr_{y^j}|pdr_{y^{j+1}})}{P(sl) 
P(dl|sl) P(sr) P(dr|sr)}\right]
\end{multline}
}

\end{document}